Blower Motor Resistor

The blower motor resistor is an important part to the car's heating and cooling system. Without the blower motor resistor the car will not blow heat or air on the lowest and middle settings. If you are suddenly stuck in a car that only blows air on high then you will want to fix the problem immediately. Usually replacing the blower motor resistor is a very easy job. This job can be done relatively quickly by anyone who has a few simple directions. Luckily the blower motor resistor is also very inexpensive. This is great news for anyone who has suddenly found themselves with a car that has stopped blowing air.

The car normally blows air through the blower however the controls and settings of the air are controlled by the blower motor resistor. The resistor controls are in charge of lessening the amount of air that comes through the vents. If your air is still working on the highest setting then the blower itself is still in working order. If you find that you are not getting any air at all, even on the highest setting, then chances are the blower has gone bad.

Before replacing your blower motor resistor you must figure out what type of resistor you have. There are two different types of blower motor resistors that are used in cars. If you have an older model car then chances are the blower motor resistor is using coils of wire. There are wires in varied thickness that cause resistance against the flow of air from the blower. Each speed has its own coil of wire. The lower the setting the thicker the coil will be and the higher the setting the thinner the coil will be. The newer model cars have blowers that work similarly but are transistorized. Fortunately ordering a new blower motor resistor is easy and costs very little. Paying a mechanic to order the part and install it will be a bit more expensive however if you are unsure how to do the job correctly this may be the best option. Installing the blower motor resistor on your own will eliminate the cost of labor and you will also get a cheaper price on the part itself.

The blower motor resistor is located under the dash board on the passenger side of the car. If you were to lay down in the floor board and look up under the dash you would be able to see the resistor and remove it quite easily. Make sure you know about removing the blower motor resistor before beginning. You should never remove any part of a car without detailed instructions on how to do this properly. You will also want to make sure to have any necessary tools handy before beginning the job. Once you have the proper installation instructions along with the proper tools, it should take an hour or less before you have a new blower resistor installed. If you install your new blower motor resistor and the controls are still not working properly then you may not have it installed correctly, you may have the wrong type of resistor or there is something else wrong within the blowing system.

If you are inexperienced with cars and the heating and air system on your car then you should then get a professional opinion. There are other car parts that may need repaired in order to get your blower working properly.

Once your blower motor resistor is replaced and the new one is working properly try not to run your heating and air condition on the lowest setting too often. Since the lowest settings offer the most resistance to the air flow you run the risk of burning out the blower motor resistor quicker by using these settings.

There Are 4 Responses So Far. »

  1. I installed a new blower motor resistor on my 1999 Tahoe, the old one did not work at the low speeds only on the high speed. I did notice that sometimes when I turned the blower motor on at the higher speed, the blower motor made a grinding sound which would go away if I turned the speed control switch off and on. The new blower motor resistor worked fine for a day, then it smoked, burned out and would not work any more. The new one worked like the old one. What do you think would have caused this problem and how would you suggest I check it and repair it? Thank you!

  2. It could be that the blower wheel, made of plastic, has split and when the motor spins at high speed, centrifugal force causes the wheel to splay out and begin striking the housing. Happened on my Cadillac. Connect a couple of wire ties together and make a band around the exterior of the blower wheel and that will solve the problem.

  3. The blower motor resistor (BMR) is only one component which can cause fan troubles. The largest component is the blower motor itself. When they get old, or corrode in wet environments, or if the airbox drain isn't clear, a blower motor can develop more resistance to rotation. This puts a higher electrical load on both the BMR and the fan switch, as well as related wiring.

    In some cases, if a BMR has overheated and gone bad, the root cause is the blower motor itself. In other cases, the additional load can cause the fan switch itself to overheat or even start smoking.

    You can check the blower motor by removing it and checking to see that it turns freely. If it's difficult to turn, is rusted, smells burned or the bearings turn rough, it needs replacement. If you do replace a blower motor, consider replacing the blower motor resistor along with it.

    Also just a note, in this article, the BMR is NOT always found under the dash on the passenger side. It varies from car to car. Check your service manual for the correct location...

  4. @ Chuck - Do not place wire ties around the fan to hold it together. That kind of shade-tree repair might work for a very short time, but is only postponing the inevitable, and could leave you stranded on a cold, damp night without a defroster.

    Also the tolerances between the fan housing and fan drum are often very tight, so placing zip ties or wire ties on there may cause the fan to stop turning altogether, resulting in a burned out fan motor or resistor.

    Go to the dealer and order a new part. Those plastic fan drums are pretty inexpensive - usually under $20. Well worth it...